Preterm birth (PTB) and spontaneous abortion (SAB) are common adverse pregnancy outcomes which account for a significant amount of maternal and infant morbidity worldwide. Although ascending genital tract infection has been implicated in approximately half of spontaneous PTB (sPTB) cases and has been linked in some studies with SAB, the microbiologic etiology of these adverse pregnancy outcomes remains poorly understood. The overall goal of our study is to determine the role of pre-pregnancy and prenatal vaginal infections with Mollicutes including fastidious Mycoplasma genitalium (MG) and the newly differentiated Ureaplasma spp. termed U. urealyticum (UU) and U. parvum (UP) in PTB and SAB. Despite the demonstrated ability of MG to infect the upper genital tract and cause pelvic inflammatory disease, very little is known about the effect of MG in pregnancy. Studies assessing the association of ureaplasmas with adverse pregnancy outcomes have been conflicting, yet are confounded with the realization that the ureaplasmas formerly called U. urealyticum were actually composed of two distinct species, UU and UP. Indeed, UU has been associated with nongonococcal urethritis in men, whereas UP has been shown in several NGU studies to be nonpathogenic. Similarly, our group was the first to recently report that UU, but not UP is associated with endometritis in women. As little is known about the effect of MG and differentiated Ureaplasma spp. on pregnancy outcomes, we propose to test the hypothesis that women testing positive for MG, UU, and UP will have increased risks of adverse pregnancy outcomes, including STB and PTB. Further, we hypothesize that the relationships between infection and pregnancy outcomes will be strongest for women with persistent infections, co-infections, and greater bacterial load. Additionally, we will examine chorioamnionitis as a mediating factor between each bacteria and spontaneous PTB. To achieve this, we propose the first comprehensive study of MG and the newly differentiated Ureaplasma spp. utilizing quantitative PCR to assess exposure at various time-points during pregnancy as well as the pre-pregnancy period among 151 women who delivered preterm, 141 women who experienced a SAB, and 302 control women who delivered at term, nested within the prospective Longitudinal Indian Family HEalth (LIFE) Study conducted in collaboration by SHARE India and the University of Pittsburgh in a rural region near Hyderabad, India. In the longitudinal cohort parent study, 1227 women were recruited before pregnancy and followed through conception, pregnancy, delivery and postpartum, and vaginal specimens were archived pre-pregnancy, at 5 weeks gestation, at first and second trimester visits, delivery and postpartum. A major innovation is our design within an Indian population which attempts conception soon after marriage allows us to feasibly and efficiently study pre-pregnancy exposures. This design is also particularly novel for the study of SAB, which has been traditionally plagued by the inability to feasibly recruit a population based sample of women pre-conception or very early in pregnancy, before many SABs occur. Our study is important, as MG and Ureaplasma infections are common, screening is not routine, and interventions based on our findings may prevent significant pregnancy morbidity in India, the U.S., and elsewhere. Further, as ureasplasmas are common in the vaginal flora of asymptomatic women who deliver to term as well as women who experience adverse pregnancy outcomes, screening for undifferentiated and unquantified ureaplasmas in the general population is unlikely to have any utility. By determining whether the risks of SAB and PTB differ by specie or bacterial load and utilizing vaginal samples collected at multiple pregnancy time points, findings from our research will be readily translated into clinical practice through screening of specimens collected non-invasively and early enough to allow for effective intervention.